<<<<<<< HEAD
var arr = [1, 2, 3, 4, 5, 6, 7];
var res = arr.unshift(0);
console.log(res);

var arr = [1, 2, 3, 4, 5];
var bal = arr.shift();
console.log(arr);
console.log(bal);

var arr = [1, 2, 3, 4, 5, 6, 7];
var del = arr.pop();
console.log(del);
=======

//整数数据类型
 var a = 1;
 console.log(a);
//NaN:非数据类型，特点：涉及到任何关于NaN的操作，都会返回NaN，而且NaN不等于自身。代码如下
let name = 'luer';
console.log(name/10); //输出为NaN
 console.log(NaN === NaN); 
 console.log(isNaN(NaN));//返回值为true

 //变量值可以改变
 let str = 2;
 str = 123;
 console.log(str);
// 在方法里不能调用，会出现Uncaught ReferenceError: user is not defined错误，
 function fn()
 {
 let user = '璐儿'
 let b = 18;
 }
//  console.log(b);
//  console.log(user);


//数组的运用，当超过数组的索引时
let arr =new Array(5,10,35,40,61);
console.log(arr[5]);  //undefined
  
//
//用use strict声名
"use strict";
 a = "你好，世界！！";
 console.log(a);

 //
let percoin = 
 {
  user:"lulu",
  age:18,
  love:"kun",
  address:"beitun"
 } 
console.log(percoin.age);
 //typeof()查看变量的数据类型

let ad = 1;
let de = "b";
let we = function(){};
let o = true;
console.log(typeof(ad));
console.log(typeof(de));     
console.log(typeof(we));
console.log(typeof(o));
>>>>>>> 05cade1c98d76717abe0b2c32d2d16e2ec6ce88f
